Steam generator



Aug. 23, 1966 w. E. GLAUssER ET Al. 3,267,907

- STEAM GENERATOR Original Filed Dec. 5, 1960 4 Sheets-Sheet l WA Y/VE E. 6.4140555@ APL /v U/VQ// Eig/V020 JT GE7Z. Je

IN VEN TORS BY uw Aug. 23, 1966 w. E. GLAUSSER ET AL 3,267,907

STEAM GENERATOR Original Filed Dec. 5. 1960 4 Sheets-Sheet 2 #076/75 Y n n 25 /6 WA yA/E 5 @405559 @fe/m2@ 62072, Je.

IN V EN TORS Aug 23, 1966 w. E. GLAUSSER ET AL 3,267,907

STEAM GENERATOR Original Filed DeQ. 5, 1960 4 Sheets-Sheet 3 //7 57E/QM 007 @CEQA/9750 WAYNE E 64' ,4Z/555.@ STEAM Allg. 23, 1966 W. E, GLAUSSER ET AL 3,267,907

STEAM GENERATOR 4 Sheets-Sheet Original Filed Dec.

INVENTY-)RS Fr. /Q

United States Patent() 3,267,907 STEAM GENERATOR Wayne E. Glausser, Arcadia, Carl H. Unruh, Pasadena, and Bernard I. Grotz, Jr., Arcadia, Calif., yassignors to C. F. Braun & Co., Alhambra, Calif., a corporation of California Continuation of application Ser. No. 73,615, Dec. 5, 1960. This Vapplication Aug. 27, 1963, Ser. No. 304,939 19 Claims. (Cl. 122-34) This application is a continuation of -our application Serial No. 73,615, filed December 5, 1960 and now abandoned.

This invention relates to heat exchange apparatus and is particularly directed to improvements in steam generators which are constructed to use hot gases in large volume as a source of heat. Steam generators embodying this -invention have been found especially useful for producing steam by utilizing a liow of hot gas issuing from a nuclear reactor.

An object of this invention is to provide a steam gener-ator comprising a heat exchanger of the shell-andtube type wherein a single bundle of tubes includes both straight tubes and U-bend tubes, or all U-bend tubes. Hollow spheres with integral tube sheets serve as the steam drum and the floating head. The hot gases at inlet temperature do not impinge directly on the outer shell. Instead, internal metallic shrouds direct the hot gases across the straight tubes and U-tubes in either single pass or multiple pass. Not until the gases have given up a large part of their heat to the tube bundle are the gases discharged into the outer shell.

Another object is to provide a steam generator in which the superheater tubes, evaporator tubes and economizer tubes are all contained in a common vertical tube bundle Y' enclosed within a shroud, and wherein the hot gases pass horizontally across the tube eld. This construction is superior to the conventional horizontal tube construction wherein undesirable high superheater tube metal temperatures and steam temperatures are produced during periods of very low gas ow. With the vertical tube bundle construction embodying this invention, thermal recirculation currents are set up at very low gas iiow rates and these currents serve to cool the superheater steam and lower the hot gas temperature, thereby preventing excessive tube metal and steam temperatures.

Another object is to provide a steam generator of this general type having a single downcomer tube extending between the steam drum sphere and the floatinghead sphere for conducting recirculating water therebetween. The downcomer tube reduces the area for flow of the hot gases, thereby producing higher velocity and maintaining higher heat density as the gases cool. The downcomer tube also serves as an access tube between the two spherical vessels.

Other and more detailed objects and advantages will appear hereinafter.

In the drawings:

FIGURE 1 is a side elevation showing one embodiment of this invention.

FIGURE 2 is a sectional side view taken substantially on the lines 2 2 as shown in FIGURE 1.

FIGURES 3, 4, 5, and 6 are sectional plan views taken substantially -on lines 3 3, 4 4, 5 5, and 6 6, respectively, as shown in FIGURE 2.

FIGURE 7 is a sectional side elevation showing a moditied form of this invention.

FIGURES 8, 9, and l0 Iare sectional plan views taken substantially on lines 8 8, 9 9, and 10-10, respectively, as viewed in FIGURE 7.

Referring to the drawings, the upright shell or pressure vessel 10 is carried by a suitable support 11. The shell 3,267,967 Patented August 23, 1966 ice 10 is generally cylindrical in shape, hav-ing rounded ends or domes 12 and 13. The dome 12 `is integrally joined with the tubesheet 14. Also integrally joined with tubesheet 14 is the hollow sphere 15 which serves as the steam drum. This construction is similar to that shown in the Haight Patent No. 2,919,906.

The tube bundle generally designated 16 extends from the tubesheet 14 to the floatinghead tubesheet 17, which is integrally joined with and forms a part of the hollow spherical oatinghead 18. All of the evaporator tubes 20 and some of the economizer tubes, designated 21, are straight tubes and are attached to both the steam drum tubesheet 14 and to the oatinghead tube-sheet 17. The superheater tubes 22 and some of the economizer tubes. designated 23, which comprise the first passes, are U-bend tubes extending upward from the oatinghead tubesheet 17. A single large diameter downcomer pipe 25 is located within the tube bundle and is connected to both tubesheets 14 and 17.

Internal shrouds direct the liow of hot gases across and through the tube bundle 16 in a single pass. The ske'leton structure of the tube bundle 16 is supported on the floatinghead tubesheet 17 and is free to expand in relation to the shell 10 and tube bundle 16. The bundle skeleton 26 includes the curved perforated plate 27, the ow directing shrouds 28 and 29, and the horizontal tube support plates 3d. The inlet pipe 31 for hot gases connects to the distribution shroud 28 through a duct 32 provided with expansion joints 33. The straight evaporator tubes 20 and the downcomer 25 pass through a horizontal plate 34 at the top of the skeleton 26 and the U-bend tubes 22 and 23 are contained within the skeleton 26. The evaporator tubes 20 land the downcomer 25 operate at about the same temperature and have very little tendency for differential expansion.

It will be noted that the tube bundle 16 is not concentrically mounted Within the shell 10, but is displaced laterally away from the inlet pipe 31. Similarly, the vertical downcomer 25 is displaced laterally in the same direction from the 'central axis of the shell 10 and also from the central axis of the tube bundle 16.

The hot gases entering the inlet pipe 31 strike the perforated plate 27, thereby preventing direct impingement on the tubes 22, and the shroud 28 provides good distribution of the hot gases along the length of the tube bundle 16. The shroud 29 directs the flow of hot gases across and through the tube bundle 16. The gases then flow through the longitudinal opening 29a in the shroud 29 and into the annular space 35 (see FIGURE 5) between the shroud 29 and the shell 10, and to the outlet duct 36 mounted on the shell 10.

Feedwater enters the inlet pipe 37 (see FIGURE 6) and passes through curved pipe 37a to the floatinghead 18. The feedwater makes several passes through the U-bend economizer tubes 23 and then one pass through the straight economizer tubes 21 up to the steam drum 1S. In the steam drum, feedwater is directed across a Contact tray 38 to wash entrained solids from the steam. The feedwater mixes with recirculating water and ows through the downcomer 25 back into the iioatinghead 18. Water enters the evaporator tubes 20 in the floatinghead 18, and the water boils as it rises to the steam drum 1S. Water recirculates through the downcomer 25. The steam passes through the perforated wash tray 38 and through mechanical separators 39 and 40 to the steam outlet 41 at the top of the steam drum sphere 15. The dry and saturated steam issuing through outlet 41 liows through an external pipe (not shown) to the inlet 42 connected to the oatinghead 18. The steam makes two or more passes through the U-bend superheater tubes 22 and leaves at the bottom of the unit through outlet duct 44, curved pipe 45 (see FIGURE 6), and through the steam outlet pipe 46.

It will be observed that the downcomer 25 has several important functions. It provides a channel for the recirculating water to ow from the steam drum to the oatinghead 18. Its position in the tube iield serves to accomplish tlow rate acceleration for the hot gases as their temperature drops while passing through the tube bundle 16. The downcomer also provides access to the interior of the floatinghead 18, since it is made large enough to permit a man to pass through the interior thereof from the upper sphere 15 to the lower sphere 18. The upper sphere 15 has a removable closure 47, which is large enough to permit a man to enter the interior of the steam drum 15.

In some cases it may not be desirable to use the downcomer 25 as a means for access to the interior of the floatinghead 18. In such case, a special access tube 50 is provided at the bottom of the floatinghead 18 and extends through the bottom dome 13 of the shell 10 by means of an expansion joint 51. The access tube 58 is provided with a flanged and bolted coverplate 52.

The use of the hollow spherical vessels 15 and 18 with integral tubesheets 14 and 17, respectively, provides important advantages. Among these are that space is provided for interpass chambers in the economizer and superheater sections. The superheater interpass chamber can be thermally isolated from the walls of the pressure sphere. Tubesheet terminals are provided for the steam generating tubes. Space is provided for water storage and for steam and water separation. The lower spherical vessel 18 is a oating header. It is not directly attached to the pressure vessel 10 containing the hot gases, and it is free to expand With relation thereto. The metal shrouds 28, 29 act as a oating thermal sleeve to permit operation of the pressure vessel 10 at a lower temperature than the temperature of the hot gases entering the inlet pipe 31. The shrouds -contain the hot gases and distribute them to obtain uniform flow to all parts of the tube bundle 16.

The combination of U-bend tubes and straight tubes in the same tube bundle have the following advantages:

The U-bend tubes prevent high stresses `caused by differential expansion in the tubes and in the tube-end joints in the economizer and superheater sections. The straight tubes in the evaporator section interconnect the spherical vessels 15 and 18 and provide support for the vessel 18. The U-bend tubes and the straight tubes are arranged so that the hot gases flow counter-current thermally to the ow of water and steam.

In the modified form of the invention shown in FIG- URES 7-10, the construction is such that two gas-flow passes are provided through the tube bundle, rather than the single pass as shown in the construction of FIGURES 1-6. Many construction features are similar in both forms of the invention.

The vertical steam generator shown in FIGURE 7 includes an upright cylindrical shell 110 integrally joined at its upper end 112 to the hollow spherical steam drum 115. The tubesheet 114 is integrally connected to the steam drum 115 and the tube bundle 116 extends downward from the tubesheet 114 to the tubesheet 117 of the oatinghead 118. The oatinghead 118 is also formed as a hollow spherical member and is integrally joined to the tubesheet 117.

, Hot gas coming from a source such as a nuclear reactor enters the inlet 131 and passes through the duct 132 and against the perforated impingement plate 127. This prevents the high velocity gases from impinging directly on the tubes of the tube bundle 116, and it helps provide for uniform distribution of gas 'along the length of the -tube bundle. The hot gases are directed by the internal shrouds 128 and flow first across the superheater tubes 122 and then across the lower half of the evaporator tubes 120. Shrouds 129'c0nfine a lateral tlow of gas through the tube bundle 116. The gases then rise through the yspace within `the shroud 130 and pass above the horizontal plate 126 which is xed to the upper limits of the shroud 128. The gases then flow laterally from right to left, as viewed in FIGURE 7, across and through the tube bundle 116 and into the interior `of the shell 110. The cooled gas flows down the annular space between the shell and the shroud 128 to the outlet duct 136 near the lower end of the shell 110.

The external steam reheater 105 may be used for the reheat cycle. Hot gas is delivered to the inlet pipe 106 and emerges from the outlet 187 after giving up some of its heat passing through t-ubes, not shown, contained within the reheater. The gases passing through the outlet 107 join with the gases leaving the lower half of the evaporator tubes within the shell 110. The combined streams of hot gases ow across the upper half of the evaporator and then across the economizer tubes 123.

The feedwater enters the inlet 137 at the steamdrum 115 and enters the economizer tubes 123. The feedwater flows up and down through the U-bend tubes 123 in the general direction counter-current to the flow of the hot gases. After the feedwater is heated to a boiling temperature, it flows across as vapor-liquid'contaet tray 138 and then mixes with .the recirculating feedwater. The recirculating feedwater ows through a plurality of upright downcomer pipes 125 to the oatinghead sphere 118 where it enters the evaporator tubes 120. The evaporator tubes 120 are straight and extend between the tubesheets 114 and 117. The steaming mixture rises in the evaporator tubes 120 to the steam drum 115. The liquid recycles to the downcomers 125, and the steam goes to the wash tray 138 to contact incoming feedwater and reduce the entrained solids -in the steam. The steam then ows through two mechanical steam separation units 139 and 140 to remove entrained water. Dry and saturated steam leaving the steam drum at the outlet 141 tiows through an external pipe (not shown) and enters the floatinghead 118 through the steam inlet 142. Steam flows up and down through the U-bend superheater tubes 122 countercurrent to the hot gases and leaves at the bottom of the unit through outlet 146.

The shrouds 128 and 130 direct flow of hot gases across and through the tube bundle 116 and prevent the hot gases from coming into direct contact with the shell 110. All of the shrouds are supported on the oatinghead 118 and are free to expand in relation to the shell 110 and the tube bundle 116. The portions of the shroud 128 in contact with the hottest of gases may be constructed of double-thickness plate to reduce heat loss and to limit transfer of radiant heat to the shell 110.

The superheater tubes 122 and the economizer tubes 123 are U-bends to provide for dilerential expansion.

The superheater channel is enclosed Within the floatinghead 118 and is entirely surrounded by saturated steam. With this design, the hot superheater channel 160 can be designed for differential pressure. Also, the highpressure oatinghead sphere 118 can be designed for relatively low temperature. The superheater outlet 161 leaves the sphere 118 through a thermal sleeve to protect the sphere from high temperature.

Having fully described our invention, it is to be understood that we do not Wish to be limited to the details set forth above, but our invention is of the full scope of the appended claims.

We claim:

1. In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, an upright bundle of generally parallel fluid-carrying tubes positioned'within said shell, at least some of the tubes having ends fixed to said tubesheet, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means within said shell connected to said inlet pipe and enclosing at least a portion of said tube bundle to direct hot gas from said inlet pipe to flow substantially in a lateral direction within said shroud means across and through said tube bundle at least once before contacting the interior yof said shell, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from the interior of the shell w-hile preventing further contact between said gas and said tubes.

2. In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, an upright bundle of generally parallel fluidcarrying tubes positioned within said shell, said bundle including evaporator tubes and superheater tubes, means connecting said evaporator tubes to said superheater tubes for serial fiow therethrough, .at least some of the tubes having ends fixed to said tubesheet, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means Within said shell connected to said inlet pipe and enclosing at least a portion of said tube bundle to direct -hot gas from said inlet pipe to fiow substantially in a lateral direction Within said shroud means across and through said tube bundle at least once before contacting the interior of said shell, said hot gas first contacting the superheater tubes and then contacting the evaporator tubes, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from the interior of the shell while preventing further contact between said gas and said tubes.

3. In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, an upright bundle of generally parallel fluid-carrying tubes positioned within said shell, said bundle including economizer tubes and evaporator tubes, means connecting said economizer tubes to said evaporator tubes for serial flow therethrough, at least some of the tubes having ends fixed to said tubesheet, the shell having a lateral inlet pipe for hot gas located adjacent one side of said ltube bundle, shroud means within said shell connected to said inlet pipe and enclosing at least a portion of said tube bundle to direct hot gas from said inlet pipe to flow substantially in a lateral direction within said shroud means across Iand through said tube bundle at least once before contacting the interi-or of said shell, said hot gas first contacting the evaporator tubes and then contacting the economizer tubes, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from the interior of the shell While preventing further contact between said gas and said tubes.

4. In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, an upright bundle of generally parallel fluid-carrying tubes positioned within said shell, said bundle including economizer tubes, evaporator tubes and superheater tubes, means connecting said tubes for serial flow therethrough in the order named, at least some of the tubes having ends fixed to said tubesheet, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means within said shell connected to said inlet pipe and enclosing at least a portion of said tube bundle to direct hot gas from said inlet pipe to flow substantially in a lateral direction within said shroud means across and through said tube bundle at least once before contacting the interior of said shell, said hot gas first contacting the superheater tubes, next the evaporator tubes and then the economizer tubes in that order, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed `across said tubes, to said outlet pipe from the interior of the shell while preventing further contact between said gas and said tubes.

5. In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, an upright bundle of generally parallel fiuid carrying tubes positioned within said shell, at least some of the tubes having ends fixed to said tubesheet, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means within said shell having a distributor connected to said inlet pipe and having a shroud element enclosing said tube bundle and provided with a longitudinal discharge opening, said shroud means acting to direct hot gas from said inlet pipe to flow substantially in a lateral direction within said shro-ud means across and through said tube bundle at least once before contacting the interior of said shell, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from the interior of the shell while preventing further contact between said gas and said tubes.

6. In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, an upright bundle of generally parallel fluid-carrying tubes positioned within said shell, at least some of the tubes having ends fixed to said tubesheet, the shell having a lateral inlet pipe for hot gas located adjacent one side Aof said tube bundle, and an outlet pipe for discharging cooled gas from said shell, shroud means within said shell to direct -hot gas from said inlet pipe to iiow substantially in a lateral direction within said shroud means across and through said tube bundle at least once before contacting the interior of said shell and to direct gas, which has passed across said tubes to `said outlet pipe from the interior of the shell while preventing further contact between said gas and said tubes, said shroud means including a shroud element enclosing the tube bundle and having a longitudinal discharge opening, said shroud means also having a curved distributor diametrically opposed from said longitudinal discharge opening, said distributor being fixed to said inlet pipe and positioned to direct hot gas into said shroud element.

7. In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, a second tubesheet mounted within the shell, an upright bundle of generally parallel tubes positioned within said shell, some of said tubes being connected to both of said tubesheets, a downcomer pipe extending between the said tubesheets within said tube bundle, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means Within said shell connected to said inlet pipe and enclosing said tube bundle and said downcomer pipe to direct hot gas from said inlet pipe to fl-ow substantially in a lateral direction within said shroud means across and through said tube bundle before contacting said shell, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from the interior of the shell while preventing further Contact between said gas and said tubes.

8. In a steam generator, the combination of: an upright shell, a steam drum supported on the upper end of said shell and comprising a hollow member having a tubesheet connected integrally therewith, an upright bundle of generally parallel tubes positioned within said shell, a hollow oatinghead positioned within the lower portion of said shell and having a floatinghead tubesheet connected integrally therewith, some of said tubes being connected to both of said tubesheets, a downcomer pipe within said tube bundle, said tubes and said downcomer pipe communicating between the interior of the steam drum and the interior of the floatinghead, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means within said shell oonnected to said inlet pipe and enclosing said tube bundle and said downcomer pipe to direct hot gas from said inlet pipe to iliow substantially in a lateral direction within said shroud means across and through said tube bundle before contacting said shell, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from the interior of the shell While preventing further contact between said gas and said tubes.

9. In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, a second tubesheet positioned within the shell, an upright bundle of generally parallel tubes positioned within said shell, a downcomer pipe extending between the tubesheets with-in said tube bundle, said tube bundle including straight evaporator tubes having opposite ends fixed tosaid tubesheets, said bundle also including U-bend superheater tubes each having both ends lixed to only one of said tubesheets, means connecting said evaporatortubes and said superheater tubes for serial flow therethrough, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means within said shell connected to said inlet pipe and enclosing said tube bundle and downcomer pipe to direct hot gas from said inlet pipe to ow substantially in a lateral direction within said shroud means across and through said tube bundle before contacting the interior of said shell, said hot gas tirst contacting the superheater tubes and then contacting the evaporator tubes, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from the interior of the shell while preventing further contact between said gas and said tubes.

1t). In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, a second tubesheet positioned within the shell, an upright bundle of generally parallel fluid carrying tubes positioned Wit-hin said shell, a downcomer pipe extending between the tubesheets within the tube bundle, said tube bundle including straight evaporator tubes having opposite ends xed to said tubesheets, said bundle also including U-bend economizer tubes each having both ends xed to only one of said tubesheets, means connecting said economizer tubes and said evaporator tubes for serial flow therethrough, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means within said shell connected to said inlet pipe and enclosing said tube bundle and downcomer pipe to direct hot gas from said inle-t pipe to ilow substantially in a lateral direction within said shroud means across and through said tube bundle before contacting the interior of said shell, said -hot gas rst contacting the evaporator tubes and then contacting the economizer tubes, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe trom the interior of the shell while preventing further contact between said gas and said tubes.

11. In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, a second tubesheet positioned within the shell, an upright bundle of generally parallel duid-carrying tubes positioned within said shell, -a downcomer pipe extending between the tubesheets within the tube bundle, said tube bundle having straight evaporator tubes having opposite ends xed to said tubesheets, said bundle also including U-bend superheater tubes Iand U-bend economizer tubes having both ends fixed to said second tubesheet, means connecting said economizer tubes, evaporator tubes and superheater tubes for serial flow therethrough in the order named, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means within said shell connected to said inlet pipe and enclosing said tube bundle and downcomer pipe to direct hot gas from said inlet pipe to ilow substantially in a lateral direction within said shroud means across and through said `tube bundle before contacting the interior of said shell, said hot gas contacting the superheater tubes, the evaporator tubes and the economizer tubes in the order named, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from, the interior of the shell while preventing further contact between said gas and said tubes.

12. In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, an upright bundle of generally parallel tubes positioned within said shell, at least some of said tubes being connected to said tubesheet, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means within the shell connected to said inlet pipe and enclosing said tube bundle to direct hot gas from said inlet pipe to ow substantially in a lateral direction within said shroud means in a :first pass across and through said tube bundle, then longitudinally within the shroud means, and then substantially in a lateral direction within said shroud means in a second pass across and through the tube bundle, all before the hot gas contacts said shell, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from 'the interior of the shell while preventing further contact between said gas and said tubes.

13. In a steam generator, the combination of: an upright shell, means including a tubesheet closing the upper end of said shell, a second tubesheet mounted within the shell, an upright bundle of generally parallel tubes positioned within said shell, at least some of said tubes being connected to both of said tubesheets, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means within the shell connected to said inlet pipe and enclosing said tube bundle to direct hot gas from said inlet pipe to ow substantially in a lateral direction within said shroud means in a rst pass across and through said tube bundle near one of said tubesheets, then longitudinally within the shroud means, and then substantially in a lateral direction within said shroud means in a second pass across and through the tube bundle near the other of said tubesheets, .all before the hot gas contacts said shell, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from the interior of the shell while preventing further contact between said gas and said tubes.

11i. In a steam generator, the combination of: an upright shell, a steam drum supported on the upper end of said shell and comprising-a hollow member having a tubesheet connected integrally therewith, an upright bundle of tubes positioned Within said shell, a hollow oatinghead positioned within the lower portion of said shell and having a oatinghe-ad tubesheet connected integrally therewith, some of said tubes being connected to both of said tubesheets downcomer pipes positioned within the shell and outside said bundle of tubes and connected to the steam drum and iloatinghead, the later said tubes aand said down- 4corner pipes communicating between the interior of the steam drum and the interior of the iloatinghead, the shell having a lateral inlet pipe for hot gas located ladjacent one side of said tube bundle, shroud means within the shell connected to said inlet pipe yand enclosing said tube bundle to direct hot gas from said inlet pipe to ilow substantially in a lateral direction within said shroud means in a lirst pass across and through said tube bundle, then longitudinally within the shroud means, and then substantially in a l-ateral direction within said shroud means in a second pass across and through the tube bundle, all before the hot gas contacts said shell, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from the interior of the shell while preventing further contact between said gas yand said tubes.

15. In a steam generator, the combination of: an upright cylindrical shell, a steam drum supported on the upper end of said shell Iand Icomprising a hollow spherical member having a circular tubesheet connected integrally therewith, an upright bundle of tubes positioned within said shell, a hollow spherical oatinghead positioned within the lower portion of said shell and having a circular oatinghead tubesheet connected integrally therewith, some of said tubes being connected to both of said tubesheets, downcomer pipes positioned within the shell and outside said bundle of tubes and communicating between the interior of the steam drum and the interi-or of the oatinghead, the shell haiu'ng a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means within the shell connected to said inlet pipe and enclosing said tube bundle to direct hot gas from said inlet pipe to flow substantially in a lateral direction within said shroud means; in a irst pass across and through said tube bundle near one of said tubesheets, then longitudinally within the shroud means, and then substantially in a lateral direction within said shroud means; ina second pass across and through the tube bundle near the other of said tubesheets, all before the hot gas contacts said shell, and an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from the interior of the shell while preventing further contact between said gas and said tubes.

16. In a steam generator, the combination of: an upright cylindrical shell, a steam drum supported on the upper end of said shell and comprising a hollow spherical member having a circular tubesheet connected integrally therewith, an upright bundle of tubes positioned within said shell, a hollow spherical oatinghead positioned Within the lower portion of said shell and having Ia circular floating head tubesheet connected integrally therewith, said bundle of tubes including evaporator tubes connected to both of said tubesheets, economizer tubes comprising U-bends connected to the first said tubesheet, and superheater tubes comprising U-bends connected to the oatinghead tubesheet, downcomer pipes positioned within the shell and outside said bundle of tubes, said tubes and said downcomer pipes communicating between the interior the steam drum and the interior of the iloatinghead, means connecting the enonomizer tubes, evaporator tubes and superheater tubes for serial liow therethrough, the shell having a lateral inlet pipe for hot gas located adjacent one side of said tube bundle, shroud means within the shell connected to said inlet pipe and enclosing said tube bundle to direct hot gas from said inlet pipe to ow substantially in a lateral direction within said shroud means in a rst pass across and through said tube bundle near one of said tubesheets, then longitudinally within the shroud means, and then substantially in a lateral direction Within said shroud means in a second pass across and through the tube bundle near the other of said tubesheets, and all before the hot gas contacts said shell, an outlet pipe for discharging cooled gas from said shell, said shroud means being positioned to direct gas, which has passed across said tubes, to said outlet pipe from the interior of the shell while preventing further contact between said gas and said tubes.

17. A steam generator as dened in claim 7, wherein the shroud means and tube bundle are non-concentrically disposed in the shell.

18. A steam generator as deiined in claim 7, wherein the downcomer pipe is non-concentrically disposed in both the shroud means and the shell.

19. A steam generator as defined in claim 7, wherein the shroud means and tube bundle are non-concentrically disposed in the shell, and wherein the downcomer pipe is non-concentrically disposed in both the shroud means and the shell, and wherein the non-concentric disposition of the shroud means and tube bundle, and the non-concentric disposition of the downcomer pipe are effected by lateral displacement thereof in a direction away from the inlet pipe,

References Cited bythe Examiner UNITED STATES PATENTS 2,336,832 12/ 1943 Badenhausen 122-34 2,922,404 l/ 1960 Kopp et al 122-34 3,114,353 12/1963 Sprague 122-34 3,154,140 10/ 1964 Esselman et al 122-34 FOREIGN PATENTS 1,197,675 6/ 1959 France.

841,800 7/ 1960 Great Britain.

KENNETH W. SPRAGUE, Primary Examiner.

PERCY L. PATRICK, FREDERICK L. MATTESON,

JR., Assistant Examiner. 

1. IN A STEAM GENERATOR, THE COMBINATION OF: AN UPRIGHT SHELL, MEANS INCLUDING A TUBESHEET CLOSING THE UPPER END OF SAID SHELL, AN UPRIGHT BUNDLE OF GENERALLY PARALLEL FLUID-CARRYING TUBES POSITIONED WITHIN SAID SHELL, AT LEAST SOME OF THE TUBES HAVING ENDS FIXED TO SAID TUBESHEET, THE SHELL HAVING A LATERAL INLET PIPE FOR HOT GAS LOCATED ADJACENT ONE SIDE OF SAID TUBE BUNDLE, SHROUD MEANS WITHIN SAID SHELL CONNECTED TO SAID INLET PIPE AND ENCLOSING AT LEAST A PORTION OF SAID TUBE BUNDLE TO DIRECT HOT GAS FROM SAID INLET PIPE TO FLOW SUBSTANTIALLY IN A LATERAL DIRECTION WITHIN SAID SHROUD MEANS ACROSS AND THROUGH SAID TUBE BUNDLE AT LEAST ONCE BEFORE CONTACTING THE INTERIOR OF SAID SHELL, AND AN OUTLET PIPE FOR DISCHARGING COOLED GAS FROM SAID SHELL, SAID SHROUD MEANS BEING POSITIONED TO DIRECT GAS, WHICH HAS PASSED ACROSS SAID TUBES, TO SAID OUTLET PIPE FROM TE INTERIOR OF THE SHELL WHILE PREVENTING FURTHER CONTACT BETWEEN SAID GAS AND SAID TUBES. 